Exhaust silencing system



' March 17, 1970 E. G. WILLETTE EXHAUST SILENCING SYSTEM 2 Sheets-sheaf 1 Filed March 13, 1969 March '17, 1970 E. s. WILLETTE EXHAUST 'SILENCING SYSTEM 2 Sheets-Sheet I Filedlarch 13, 1969 *W far/Y &- 14 1/2 'LW, 0% ya United States Patent Ofice Patented Mar. 17, 1970 3,500,954 EXHAUST SILENCING SYSTEM Earl G. Willette, Racine, Wis., assignor to Walker Manufacturing Company, Racine, Wis., a corporation of Delaware Filed Mar. 13, 1969, Ser. No. 806,964 Int. Cl. F01n 1/00 US. Cl. 181--35 9 Claims ABSTRACT OF THE DISCLOSURE Each side of a dual exhaust silencing system for automobiles has first and second silencing units interconnected by a pipe with a kick-up section to go over the rear axle of an automobile, the first section including silencing arrangements for attenuating high frequency roughness, removing sounds in the vicinity of 125 c.p.s., and lowering the overall sound level whereas the second unit attenuates miscellaneous noise and roughness having a medium frequency level.

BRIEF SUMMARY OF THE INVENTION It is the purpose of this invention to provide a highly efiective exhaust sound attenuation system which is also attractive in appearance, economical to manufacture, and small in diameter so that it fits in the restricted space available in a modern passenger automobile.

In preferred form the invention accomplishes the foregoing and other objects by means of a structure which has an elongated small diameter housing that is necked down or reduced in diameter at various longitudinal locations to provide a series of longitudinally spaced chambers that are designed to provide different sound attenuating results. The housing includes at its inlet end a pair of spit chamber arrangements of differing volumes and then the expansion chamber and this is followed by a unique restrictor type chamber at the outlet end of the housing. This housing is connected through an exhaust conduit to a second housing that provides a roughness control chamber.

DESCRIPTION OF THE DRAWINGS FIGURE 1 is a perspective view of a dual exhaust system embodying the invention with parts broken away to reveal the internal construction;

FIGURE 2 is an enlarged cross section along the line 22 of FIGURE 1;

FIGURE 3 is a cross section along the line 33 of FIGURE 2; and

FIGURE 4 is a cross section along the line 4-4 of FIGURE 2.

DETAILED DESCRIPTION OF THE INVENTION The mufiler system 1 is of the dual type having a lefthand side 3 and a righthand side 5 which are substantially identical in construction so that a description of the side 3 will suffice as an explanation of the invention. The exhaust system 3 includes an upstream silencer 7 having a housing of tubular form which is of substantially uniform diameter throughout its length and which contains certain silencing structures as will be explained hereinafter. The system 3 also includes a downstream silencing unit 9 with housing 10 which is tubular in configuration and preferably the same diameter as the housing 8 though considerably shorter in length. The units 7 and 9 are joined by a selectively bent and smaller diameter conduit 11 which in the illustrated embodiment includes an arched kick-up section 13 that will fit over the rear axle structure of the vehicle. On the downstream side of the unit 9 is attached a tailpipe spout .15 which may be chromium plated or otherwise treated to provide an attractive appearance at the outlet end which is normally exposed to view at the rear of an automobile.

The particular dual system 1 that is described herein is designed specifically for the V8 engine of a 1969 model automobile of United States manufacture and in particular removes a troublesome fifth mode of vibration which occurs at c.p.s. The anti-node for this frequency is located approximately in the center of the front unit 7.

The housing 8 for upstream silencing unit 7 is originally uniform diameter tubing but is reduced in diameter at its inlet end to form an inlet bushing 17 for attachment to an exhaust pipe leading from the exhaust manifold and at the outer end to form an outlet bushing 19 that may be secured iby clamp 21 to the upstream end of the pipe section 11. Housing 8 is also reduced in diameter at sections 23, 25, 27 and 29 by pinching U-shaped folds into the metal to form reduced diameter internal sections, such sections being tightly fitted to the internal tubing as seen in FIGURE 4. The pinched sections 23 and 25 define a chamber 31; the pinched sections 25 and 27 define an internal chamber 33 which is preferably slightly larger in volume (i.e., longer) than the chamber 31; the pinched sections 27 and 29 form a chamber 35; and the pinched sections 29 along with outlet bushing 19 form an internal chamber 37. A gas flow tube 39 is supported in the pinched sections 23, 25, and 27 and has patches of louvers 41 and 43 opening into the chambers 31 and 33, respectively, so that these chambers function as high frequency tuning chambers of different sizes for tuning different high frequency ranges and providing attenuation of roughness. The tube 39 receives gas from inlet bushing 17 and empties into the chamber 35 which is substantially larger in diameter so that it constitutes an expansion volume or chamber for gas leaving the tube 39 and acts to lower the overall sound level.

The front chambers 31 and 33 and the expansion volume 35 are located to attenuate the fifth mode of vibration for the specific engine and system length. While the anti-node moves with temperature changes it is located in the front pinch sections adjacent the end of pipe 39.

The attenuating structure present in the chamber 37 is shown in greater detail in FIGURES 2 and 3 and it will be observed that the coaxial section of the design provides cross-bleeding and turn-around effects of a standard tri-flow or overlap muffler. It includes a gas flow tube 45 that is supported by the reduced diameter inlet section 29 and by the outlet bushing 19. Approximately midway along the length of the tubing 45 is a partition 47 which is welded inside of the tube and which has a flanged opening 49 that is substantially smaller in diameter than the internal diameter of the tube 45 so that the member 47 acts as a restrictor. On the upstream side of the restrictor 47 and adjacent to it is a patch of louvers 51 opening into the chamber 37 and on the downstream side of the restrictor 47 is a louver patch 53 also opening into the chamber 37. The louver patches comprise a multiplicity of small openings which act as very small tuning tubes connecting the interior of the pipe 45 with the chamber 37.

Adjacent the upstream end of the chamber 37, the tube 45 has a pair of large diametrically opposite holes 55 opening into the chamber 37 and providing relatively little restriction to passage of gas. Similarly, adjacent the downstream end of the chamber 37 the tube 45 has a pair of oppositely located large diameter openings 57. Preferably, a substantial length imperforate portion of the tube separates the holes 55 and 57 from the adjacent louver patches as indicated at 56 and 58.

' An annular partition 59, which is substantially coplanar with the restrictor 47 and therefore located between the louver patches 51 and 53, is illustrated and is of optional use in the attenuating construction associated with chamber 37. It has a large number of angularly spaced holes 61 located around its circumference which will interconnect the upstream side of the chamber 37 that is associated with the patch 51 and the openings 55 with the downstream section of the chamber 37 that is associated with the louver patch 53 and the openings 57.

The silencing effect of unit 7 for a given diameter of chamber 37 can be varied to obtain optimum silencing by changing the size of hole 49, the sizes of holes 55 and 57, the diameter of tube 45, the sizes of louver patches 51 and 53, and the length of the chamber 37.

Referring again to FIGURE 1, the uniform diameter housing 10 of unit 9 is necked down to form an inlet bushing 65 and an outlet bushing 67, the former being welded to the outlet end of the pipe 11 and the latter being secured by the clamp 69 inside of the spout 15. A straight-through gas flow tube 71 is supported inside of the bushings 65 and 67 and has louvers fonmed around its circumference along all or a substantial part of its length as indicated at 73 to form with chamber 75 a relatively large volume roughness control tuning chamber that is effective on a wide range of frequencies.

In operation, gas enters the dual systems 5 and 7 and the spit chambers 31 and 33 attenuate different high fre quency ranges and provide roughness control. Expansion of the gas into volume 35 lowers the overall sound level as does passage through chamber 37. The structure inside chamber 37 is such as to cause turn-around flow, cross bleeding, and general turbulence and thereby remove considerable energy from the gas. Final roughness control is achieved in chamber 75. The fifth mode of vibration is removed in chambers 31, 33, and 35.

I claim:

1. A silencing device for the exhaust system of an internal combustion engine comprising an outer tubular housing having a reduced diameter inlet portion at one end and a reduced diameter outlet portion at its other end, a gas flow pipe having an inlet end supported by said inlet portion and an outlet end supported by said outlet portion, the space between the pipe and housing forming a chamber, a restrictor supported inside said gas flow pipe adjacent the midpoint thereof and having an opening therein smaller in diameter than the inside diameter of the gas flow pipe, a first patch of small openings in said pipe on the inlet side of the restrictor and a second patch of small openings in the pipe on the outlet side of the restrictor, said gas flow pipe having a first pair of relatively large openings therein adjacent its inlet end and a second pair of relatively large openings therein adjacent its outlet end.

2. A device as set forth in claim 1 including a perforated transverse partition in said chamber substantially coplanar with said restrictor.

3. A device as set for the in claim 1 wherein said first and second patches comprise a multiplicity of louvers.

4. A device as set forth in claim 1 wherein there is a substantial imperforate length of pipe separating said first pair of openings and said first patch and a substantial imperforate length of pipe separating said second pair of openings and said second patch.

5. A device as set forth in claim 1 wherein substantial lengths of imperforate pipe separate respectively said first pair of openings and first patch and said second pair of openings and second patch and wherein said first and second patches comprise a multiplicity of louvers.

6. A device as set forth in claim 5 including a perforated transverse partition in said chamber substantially coplanar with said restrictor.

7. An exhaust system for an internal combustion engine comprising an outer tubular housing having a reduced diameter inlet bushing and a reduced diameter outlet bushing, a first gas flow pipe having an inlet end supported in said inlet bushing, said housing having first and second reduced diameter portions extending radially inwardly to said pipe and defining with said pipe first and second silencing chambers, said pipe being perforated in said chambers whereby said chambers function as high frequency attenuating spit chambers, said pipe havingan outlet end supported in said second reduced diameter portion, said outer housing having a third reduced diameter portion spaced from the second reduced diameter portion and acting with it to define an expansion chamber located to receive gas leaving said first pipe, a second gas flow pipe having an inlet end supported in said third reduced diameter portion and an outlet end supported in said outlet bushing, a restrictor supported inside said second pipe and having an opening therein smaller than the inside diameter of said second pipe, said second pipe having patches of small openings located on opposite sides of said restrictor, said second pipe having relatively large openings therein adjacent its inlet and outlet ends.

8. An exhaust system as set forth in claim 7 including a second tubular outer housing having a reduced diameter inlet bushing and a reduced diameter outlet bushing, a conduit connecting the outlet bushing of the first tubular housing to the inlet bushing of the second tubular housing, and a third perforated gas flow pipe having an inlet end supported by the inlet bushing of the second housing and an outlet end supported by the outlet bushing of the second housing.

9. An exhaust system as set forth in claim 8 wherein the outlet end of said first gas flow pipe is located adjacent the anti-node of the fifth mode of vibration for the exhaust system.

References Cited UNITED STATES PATENTS 2,357,791 9/1944 Powers 18154 2,618,353 11/1952 Hedrick 18148 3,036,654 5/1962 Powers 18154 3,209,861 10/1965 Whitney 181--59 3,219,142 11/1965 Deremer 18148 3,259,206 7/1966 Straw 18159 7 3,338,331 8/1967 Jettinghoff.

ROBERT S. WARD, 111., Primary Examiner US. Cl. X.R. 18157, 59, 61, 63 

